for example,
50th bfs = 48th bfs + 49th bfs
that means, 1st portion of 50th bfs is exactly same as 48th bfs
so, if 48th bfs length exceeds 2^31 then you don't need to find 50th bfs
you can tell the answer of any question on 50th bfs using 48th bfs

so its enough to create upto 48th bfs … but that will exceed time and space complexity
thats why, i created upto 30 bfs, which is feasible in terms of space & time complexity